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Discussion Starter #1
I was just wondering if there are any major increases in speed from say a bullet fired out a guide gun vs. a cowboy, if so how much
 

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As a rule, shorter barrel=lower velocity. How much lower is greatly dependent on the load being used, and high-intensity magnum rounds seem to suffer a greater per-inch velocity loss than more sedate rounds. But it is important to note that as a general rule the lower velocity will make very little or no practical difference when it comes to hunting. No animal on earth will detect the difference between a 300 gr. bullet at 1900 fps and the same bullet at 1750 fps.
 

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13 - 25 fps per inch is common I believe.
 

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Discussion Starter #4
As a rule, shorter barrel=lower velocity. How much lower is greatly dependent on the load being used, and high-intensity magnum rounds seem to suffer a greater per-inch velocity loss than more sedate rounds. But it is important to note that as a general rule the lower velocity will make very little or no practical difference when it comes to hunting. No animal on earth will detect the difference between a 300 gr. bullet at 1900 fps and the same bullet at 1750 fps.
no i know, just wondering as far as trajectory and accuracy goes.
 

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Trajectory depends on a combination of bullet and speed, in a 45-70 I doubt you would ever notice a real world difference between available barrel lengths. Accuracy has nothing to do with barrel length unless your using open sights-then the added length would be an advantage.Too long of a barrel can hurt accuracy due to barrel droop, and velocity could even suffer with a faster burning powder.
 

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Greg,

Your #1 post wanted to know about "speed" and your #4 post about "trajectory" and "accuracy" given different the different barrel lenghts of a GG and a CB. Maybe you could share with us what you desiring and we could help you.
Best,
Dan
 

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Discussion Starter #7
Dan, Thanks..

well just wondering how much more speed will I gain with a longer barrel

example:

if I shoot a 400 grain bullet at say 1330 fps out of a guide gun.. can be any number but will use the standard remington 405 grainf actory cartridge, If i shot this exact same round out of a cowboy how much more speed will the bullet gain.. 1400? 1500?
 

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You may gain 100 fps, you may gain nothing. And, depending on the load, you may actually lose velocity as the bullet begins to decelerate before it can get out of the barrel.
 

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Dan, Thanks..

well just wondering how much more speed will I gain with a longer barrel

example:

if I shoot a 400 grain bullet at say 1330 fps out of a guide gun.. can be any number but will use the standard remington 405 grainf actory cartridge, If i shot this exact same round out of a cowboy how much more speed will the bullet gain.. 1400? 1500?
If you are indeed unsing the factory remington load remember the 1330 fps is from a factory 24in. barrell and it will be a bit slower in a guide gun.
 

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Dan, Thanks..

well just wondering how much more speed will I gain with a longer barrel

example:

if I shoot a 400 grain bullet at say 1330 fps out of a guide gun.. can be any number but will use the standard remington 405 grainf actory cartridge, If i shot this exact same round out of a cowboy how much more speed will the bullet gain.. 1400? 1500?
Greg,

I have chrono'd the factory Remington 405gr JSP out of my 1895 (22" ballard rifling) and average around 1,417 fps. My 1895 GG runs around 1,300 fps. I no longer use any factory ammo and solely reload hard cast lead bullets. In my 1895, I'm running the BTB 460"-425gr bullet at close to 1,900 fps (a very stout load of H335 pushing it).

Dan
 

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Greg, by now you may have realized this, but the only honest answer you can be given is that usually a longer barrel will give you somewhat higher velocity -- but not always. Furthermore, if you do get a velocity gain no one can tell you with any accuracy how much it will be.

Guns are like people. All are similar, but no two are exactly alike. Some barrels are "faster", others "slower", even if they are exactly the same length. Chamber dimensions, bore dimensions, bore smoothness -- all these factors vary, and even a tiny variation between barrels can make a measureable difference in velocity, such that sometimes a shorter barrel will shoot the same load faster than a longer one!
 

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Greg, by now you may have realized this, but the only honest answer you can be given is that usually a longer barrel will give you somewhat higher velocity -- but not always. Furthermore, if you do get a velocity gain no one can tell you with any accuracy how much it will be.

Guns are like people. All are similar, but no two are exactly alike. Some barrels are "faster", others "slower", even if they are exactly the same length. Chamber dimensions, bore dimensions, bore smoothness -- all these factors vary, and even a tiny variation between barrels can make a measureable difference in velocity, such that sometimes a shorter barrel will shoot the same load faster than a longer one!
+1. I agree. I have three 336C 35Rem's and they will differ by 100 FPS using the exact same loads.
Dan
 

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Greg:

You asked why bullets go faster (usually) out of a longer barrel. The reason that the bullet generally travels faster out of a longer barrel is because the powder keeps burning down the barrel and keeps propelling the bullet.

Now, it's been mentioned in this post that sometimes, with a certain load, you will not have an increase in velocity, and that in some, you will actually have the bullet slow down with a longer barrel. The reason for these anomalies is that not all powder burns at the same speed. If you have a really fast-burning powder, then it will burn up completely (in a light load of that powder) in a shorter barrel. In such loads, a longer barrel is not really going to produce more speed. Once the powder is burned up, there is no more combustion pushing the bullet, and the friction of the barrel will actually start to slow the bullet down (i.e., a 100 yard long barrel will shoot sower than n 18.5 inch barrel). This is why fast powders like AA 1680 and Reloader 7 will keep pretty consistent speeds in the 22" and 24" barrels of the Marlins. However, if you are using a slower powder like H4895, then you will notice some difference....especially if you are putting a lot of powder in the load.

Naturally, as the barrel's friction is what begins to slow a bullet down after the powder is burned, a gun with a "slicker" barrel will shoot faster. This is why some of the guys said that each gun is different. This is also why some people notice an increase in speed after fire-lapping their barrel...since the friction points and rough spots are removed.

You should also know that for a long time manufacturers have been loading slower powders, as it helps them get faster velocities out of the longer test barrels they use, but then we all shoot the stuff and it's a lot slower. In that regard, there are some exceptions; I believe Corbon actually uses an 18.5" barrel to test, and Double Tap uses a 22" barrel to test...Buffalo Bore may also use real guns to test their speed.
 

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Leveraging off of what Need_Medecine said, here are a couple of examples using two 357mag Rossi rifles, one a 20" barreled carbine and the other a 24" barreled rifle as well as a 7.5" Uberti Cattleman. Here is my ballistics info of all three barrel lengths. You see that you don't always get increased velocities out of a longer barrel, especially when you're discussing pistol caliber loads shot out of rifle length barrels.

First load: 38spl+P load using 13.5grn of H110, magnum primer, and a Zero 158grn JSP bullet.

7.5" Uberti Pistol: MV = 1,290fps
20" Rossi Carbine: MV = 1,496fps
24" Rossi Rifle: MV = 1,460fps

(Note that with the light charge weight, the carbine's velocity is higher than the rifle's.)

Second load: 357mag load using 16.5grn of H110, magnum primer, and a Zero 158grn JSP bullet.

7.5" Uberti Pistol: MV = 1,458fps
20" Rossi Carbine: MV = 1,789fps
24" Rossi Rifle: MV = 1,822fps

(Note that with the heavy charge weight, the rifle's velocity is higher than the carbine's.)

Third load: 38spl Cowboy load using 3.5grn of TiteGroup, std primer, and a Berrys 158grn TMJ bullet.

7.5" Uberti Pistol: MV = 733fps
20" Rossi Carbine: MV = 661fps
24" Rossi Rifle: MV = not tested for fear of bullet sticking in barrel

So what does the above data indicate? First lets look at the slow burning magnum powder H110.

1st - it's burned more completely in a 20" & 24" barrel than a 7.5" barrel as evidenced by the higher velocities.

2nd - lower charge weights (13.5grn 38spl load) completely burns up during the bullet's travel down rifle length barrels, however, with this load the bullet decelerates during the extra 4" travel in the rifle length barrel vs the 20" carbine length one.

3rd - the higher, magnum charge weight (16.5grn 357mag load) continues to accelerate the bullet down the full length of the 24" rifle's barrel as compared to the 20" carbine's

Now let's look at the much faster burning but much lighter charged pistol powder's performance.

It is clear that TiteGroup is a very fast burning powder as the velocity of the 7.5" revolver (with it's cylinder to barrel opening) is faster than the velocity obtained from a 20" carbine. This indicates that the fast burning powder burns completely well before the bullet leaves the barrel of the carbine and the bullet is actually slowing down as it leaves the muzzle.

Bottom line, the OP's original question provides insufficient specificity to answer directly until additional data is provided.

That said, generally speaking, a round with a fast burning, lower weight charge (as commonly found in a std pistol load) will not gain much velocity and if light enough charge, could actually lose velocity when shot from a rifle length barrel because the powder burns completely so fast that it doesn't continue to accelerate the bullet in the longer barrel.

That compares to a slower burning, higher weight charge (as commonly found in a magnum pistol load) which will benefit from the longer barrel length because the powder is still burning as the bullet travels farther down the longer barrel.

For the record, acceleration of a bullet isn't just a function of the peak pressure the bullet sees at ignition, but rather the total pressure accelerating the bullet as it travels down the full length of the barrel.
 

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In reference to lever action rifles and standard lever action cartridges my response is, "Not enough to make a difference."

Within the parameters of leverguns and their cartridges I think that handling characteristics are much more important than statistically insignificant difference in muzzle velocity. Choose the barrel length that feels the best to you, practice to develop marksmanship skill, and don't worry about ballistics.

I have two Marlins with 20" barrels and they work fine for me. I prefer the 22" length of my Marlin 444S because of the way it handles with the balance point just a little further forward than the carbines. My choice has nothing to do with the ballistics.
 

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My .450 Marlin guide gun runs about 100fps slower than published data for 22-24 inch barrels.

Getting the better handling characteristics of the GG is a fair trade off, IMO.
 
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